# What Is 'Transaction Dropping' and Why Does It Happen in a Congested Mempool? ⎊ Path

**Published:** 2025-12-04
**Author:** Greeks.live
**Categories:** Path

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## What Is ‘Transaction Dropping’ and Why Does It Happen in a Congested Mempool?

Transaction dropping occurs when a node removes an unconfirmed transaction from its Mempool, usually because it has been waiting too long or the fee is too low compared to newer, higher-fee transactions. In a congested Mempool, miners prioritize higher-fee transactions, causing low-fee transactions to be ignored and eventually dropped by nodes to free up memory.

The user must then resubmit with a higher fee.

- [What Is the Mempool and How Is It Exploited for Front-Running in Crypto?](https://learn.greeks.live/path/what-is-the-mempool-and-how-is-it-exploited-for-front-running-in-crypto/)

- [What Is a “Mempool” in Cryptocurrency and Why Is Its Size Important to Transaction Fees?](https://learn.greeks.live/path/what-is-a-mempool-in-cryptocurrency-and-why-is-its-size-important-to-transaction-fees/)

- [What Is the Difference between a Node’s Mempool and the Global Set of Unconfirmed Transactions?](https://learn.greeks.live/path/what-is-the-difference-between-a-nodes-mempool-and-the-global-set-of-unconfirmed-transactions/)

- [How Do Full Nodes Share Mempool Data to Improve Network-Wide Fee Estimation?](https://learn.greeks.live/path/how-do-full-nodes-share-mempool-data-to-improve-network-wide-fee-estimation/)

- [What Is a ‘Mempool’ and How Does It Relate to Transaction Fees?](https://learn.greeks.live/path/what-is-a-mempool-and-how-does-it-relate-to-transaction-fees/)

- [In a Congested Network, What Is “Transaction Latency” and Why Does It Increase?](https://learn.greeks.live/path/in-a-congested-network-what-is-transaction-latency-and-why-does-it-increase/)

- [What Happens If the Mempool Becomes Congested?](https://learn.greeks.live/path/what-happens-if-the-mempool-becomes-congested/)

- [What Criteria Must a Transaction Meet to Be Accepted into a Node’s Mempool?](https://learn.greeks.live/path/what-criteria-must-a-transaction-meet-to-be-accepted-into-a-nodes-mempool/)

## Discover More

### [How Do Replace-by-Fee (RBF) Mechanisms Help Users on a Congested Network?](https://learn.greeks.live/path/how-do-replace-by-fee-rbf-mechanisms-help-users-on-a-congested-network/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![How Do Replace-by-Fee (RBF) Mechanisms Help Users on a Congested Network?](https://learn.greeks.live/wp-content/uploads/2025/10/Interlocking-Precision-Mechanisms-Modeling-Complex-Cryptocurrency-Derivatives-Settlement-Protocols.webp)

RBF allows a user to replace a stuck, unconfirmed transaction with a new one that includes a higher fee, speeding up confirmation.

### [Why Might a Miner Prioritize a Zero-Fee Transaction over a Low-Fee One?](https://learn.greeks.live/path/why-might-a-miner-prioritize-a-zero-fee-transaction-over-a-low-fee-one/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![Why Might a Miner Prioritize a Zero-Fee Transaction over a Low-Fee One?](https://learn.greeks.live/wp-content/uploads/2025/10/Crystalline-Bifurcation-Balancing-Volatile-Digital-Asset-Swaption-Payoffs-Across-Impermanent-Loss-Vectors.webp)

A miner only prioritizes a zero-fee transaction if it is their own internal transaction or if the block space is entirely empty.

### [Why Is the Consumed Gas Not Refunded upon Transaction Failure?](https://learn.greeks.live/path/why-is-the-consumed-gas-not-refunded-upon-transaction-failure/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![Why Is the Consumed Gas Not Refunded upon Transaction Failure?](https://learn.greeks.live/wp-content/uploads/2025/10/Symmetrical-Quadrant-Divergence-Illustrating-Asymmetric-Payoff-Structure-in-Decentralized-Exchange-Liquidity-Provision.webp)

The network and validator still expended computational resources (CPU, memory) to execute the failing transaction up to the point of error.

### [Can an Oracle Itself Be Front-Run If Its Price Update Is Visible in the Mempool?](https://learn.greeks.live/path/can-an-oracle-itself-be-front-run-if-its-price-update-is-visible-in-the-mempool/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![Can an Oracle Itself Be Front-Run If Its Price Update Is Visible in the Mempool?](https://learn.greeks.live/wp-content/uploads/2025/10/Saturnine-Structure-Representing-Stochastic-Volatility-Surface-Convergence-in-Decentralized-Finance-Primitives.webp)

Yes, if the oracle's price update is visible in the mempool, a front-runner can trade against the old price before the new one is confirmed.

### [How Does a Mempool Relate to the Speed of a Transaction Confirmation?](https://learn.greeks.live/path/how-does-a-mempool-relate-to-the-speed-of-a-transaction-confirmation/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![How Does a Mempool Relate to the Speed of a Transaction Confirmation?](https://learn.greeks.live/wp-content/uploads/2025/10/Sleek-Ovoid-Blockchain-Governance-Module-Reflection-Demonstrating-Impermanent-Loss-Mitigation-Strategies.webp)

The mempool is the waiting area for unconfirmed transactions; higher fees ensure faster selection by miners and quicker confirmation.

### [Why Is Transaction Cost Simulation Important in Backtesting?](https://learn.greeks.live/path/why-is-transaction-cost-simulation-important-in-backtesting/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![Why Is Transaction Cost Simulation Important in Backtesting?](https://learn.greeks.live/wp-content/uploads/2025/10/Bespoke-Algorithmic-Trading-Mechanism-Revealing-Internal-Actuator-Dynamics-For-Decentralized-Finance-Primitives.webp)

Simulating transaction costs prevents overestimating a strategy's profitability due to real-world fees and slippage.

### [What Is "Transaction Malleability" and How Does It Relate to Congestion?](https://learn.greeks.live/path/what-is-transaction-malleability-and-how-does-it-relate-to-congestion/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![What Is "Transaction Malleability" and How Does It Relate to Congestion?](https://learn.greeks.live/wp-content/uploads/2025/10/Microcosm-of-Secured-Cross-Chain-Interoperability-Mechanisms-in-Decentralized-Finance-Layer-Solutions.webp)

The ability to change a transaction's ID before confirmation; it complicated Layer 2 solutions and was largely fixed by SegWit, indirectly easing congestion concerns.

### [What Is "Front-Running" and How Is It Exacerbated by a Large Mempool?](https://learn.greeks.live/path/what-is-front-running-and-how-is-it-exacerbated-by-a-large-mempool/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![What Is "Front-Running" and How Is It Exacerbated by a Large Mempool?](https://learn.greeks.live/wp-content/uploads/2025/10/Cryptocurrency-Derivative-Mechanism-Disassembly-Revealing-Atomic-Swap-Settlement-Infrastructure.webp)

An entity executes a trade ahead of a pending one to profit; a large mempool makes it easier for bots to identify and bid higher fees to front-run.

### [How Many Confirmations Are Typically Recommended for a Large-Value Transaction and Why?](https://learn.greeks.live/path/how-many-confirmations-are-typically-recommended-for-a-large-value-transaction-and-why/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![How Many Confirmations Are Typically Recommended for a Large-Value Transaction and Why?](https://learn.greeks.live/wp-content/uploads/2025/10/Macro-View-of-Centralized-Exchange-Lens-Reflecting-Multi-Asset-Volatility-Surface-Dynamics.webp)

Six confirmations are typically recommended for large transactions because the probability of a successful malicious chain re-org becomes negligible.

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**Original URL:** https://learn.greeks.live/learn/what-is-transaction-dropping-and-why-does-it-happen-in-a-congested-mempool/
